U.S. patent number 6,871,844 [Application Number 10/334,787] was granted by the patent office on 2005-03-29 for humidifier.
This patent grant is currently assigned to Industrial Technology Research Institute. Invention is credited to Falin Chen, Hsin-Sen Chu, Jar-Lu Huang, Keh-Chyun Tsay, Yi-Yie Yan.
United States Patent |
6,871,844 |
Yan , et al. |
March 29, 2005 |
Humidifier
Abstract
A humidifier for fuel cells includes a housing with a
heat-exchange plate formed therein, the plate defining first and
second gas passages having gas inlets and outlets, respectively; a
plurality of apertures formed on the plate; and a plurality of
reservoirs fixed under the apertures and filled with a water
absorbable and permeable stuffing material for trapping and storing
water. The water permeable stuffing material may be disposed in the
first gas passage. Cool, dry oxygen/air is channeled to the first
gas passage and conveyed to an oxygen/air inlet of the fuel cell,
and high-temperature, high-moisture exhaust gas discharged from the
fuel cell is introduced to the second gas passage, such that water
and heat of the exhaust gas in the second gas passage are recycled
by the heat-exchange plate and conveyed to the first gas passage,
thereby achieving the humidification effect and improving
electricity-generating efficiency of the fuel cell.
Inventors: |
Yan; Yi-Yie (Hsinchu,
TW), Huang; Jar-Lu (Judung Hsinchu, TW),
Tsay; Keh-Chyun (Judung Hsinchu, TW), Chen; Falin
(Judung Hsinchu, TW), Chu; Hsin-Sen (Judung Hsinchu,
TW) |
Assignee: |
Industrial Technology Research
Institute (Hsin Chu Hsien, TW)
|
Family
ID: |
31493719 |
Appl.
No.: |
10/334,787 |
Filed: |
January 2, 2003 |
Current U.S.
Class: |
261/154; 261/156;
261/99; 261/16 |
Current CPC
Class: |
H01M
8/04126 (20130101); H01M 8/04074 (20130101); H01M
8/04171 (20130101); F24F 2003/1435 (20130101); Y02E
60/50 (20130101) |
Current International
Class: |
B01F
3/04 (20060101); H01M 8/02 (20060101); B01F
003/04 () |
Field of
Search: |
;261/16,99,104,107,154,156,157,161 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bushey; Scott
Attorney, Agent or Firm: Arent Fox PLLC
Claims
What is claimed is:
1. A humidifier, comprising: a housing, including a plate having a
solid portion formed inside said housing, and defining a first gas
passage and a second gas passage by said plate, said first gas
passage and said second gas passage having gas inlets and gas
outlets respectively; a plurality of apertures formed on said
plate; a water absorbable and permeable stuffing material; and a
plurality of reservoirs for trapping and storing water, said plural
reservoirs fixed under said apertures, and said plural reservoirs
filled with said water absorbable and permeable stuffing
material.
2. The humidifier as in claim 1, wherein said gas inlet of said
first gas passage is for conveying air or oxygen therein, whereas
said gas outlet of said first gas passage communicates with an air
or oxygen inlet of a fuel cell, and wherein said gas inlet and said
gas outlet of said second gas passage are for conveying in and out
of exhaust gas respectively.
3. The humidifier as in claim 1, wherein said plate is for
exchanging heat.
4. The humidifier as in claim 1, wherein said plate is made of
metal.
5. The humidifier as in claim 1, wherein said plate is vertically
mounted.
6. The humidifier as in claim 1, wherein said water-trapping
reservoir is formed as a U-shaped structure, and at least one
water-trapping reservoir is mounted.
7. The humidifier as in claim 1, wherein the location of said
water-trapping reservoir on one side of said second gas passage is
higher than that of said aperture.
8. The humidifier as in claim 1, wherein said first gas passage is
disposed with water permeable stuffing material therein.
9. The humidifier as in claim 1, wherein an evaporation surface of
said plate facing with said first gas passage is disposed with at
least one fin thereon.
10. The humidifier as in claim 1, wherein an evaporation surface of
said plate facing with said first gas passage is coarsely
processed.
11. The humidifier as in claim 1, wherein a condensation surface of
said plate facing with said second gas passage is disposed with at
least one fin thereon.
12. The humidifier as in claim 1, wherein a condensation surface of
said plate facing with said second gas passage is hydrophobically
processed.
13. The humidifier as in claim 1, wherein said water absorbable and
permeable material is to fully fill said aperture underneath said
plate.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a humidifier, more particularly, a
humidifier applied in a fuel cell system by recycling
high-temperature and high-moisture exhaust gas discharged from the
fuel cell, and transferring water and heat acquired from the
recycling process to air or oxygen about to be drawn into the fuel
cell, thus achieving effective humidification and increasing the
efficiency of the fuel cell system.
2. Description of the Related Art
The Proton-Exchange Membrane Fuel Cell (PEMFC) consists of a
plurality of cell units, with each of the cell unit comprising the
bi-polar plate, membrane electrode assembly (MEA) and the gasket,
wherein the MEA is formed by applying a layer of catalyst and
adhering a layer of carbon cloth or carbon paper on a layer of
polymer membrane (such as Nafion manufactured by DuPont); the
bipolar plate is formed by conductive material, such as graphite,
inlayed with gas passages, which convey gas proportionally and
swiftly to the top surface of the MEA, thus generating electronic
reactions with the catalyst and electrons and other yields are
produced. Such electrons can be formed as utilizable electric
current via external bridge passageway, and other yields therefrom
(such as water and heat) are to be discharged externally via
related means.
Since fuel cells utilize reactions between hydrogen and oxygen/air
to generate power, they are considered a clean energy source, for
the only waste material discharged during such reaction process is
water and heat without any chemical or physical waste being
produced that might cause environmental or biological concerns and
would require higher costs and complicated processing procedures,
as do other types of energy-generating sources.
Volumes of electric current and power generated by fuel cells
determine the efficiency of fuel cells, and factors controlling
volumes of electric current and power generated by fuel cells then
include the design of gas passages within the bipolar plate,
effective area of the catalyst, the characteristics of polymer
membrane material, the thickness and degree of porosity for the
electrode layer, wherein the characteristics of polymer membrane
material are to separate positive and negative gas molecules and
isolate electrons but allow water molecules and hydrogen ions to
permeate, thus acquiring the effect of an electrical bridge.
Hydrogen ions need to be brought along by water molecules to
permeate through the polymer membrane, and hydrogen ions acquire
better permeation as the moisture of the polymer membrane goes
higher. Therefore, it is one of the key technologies in fuel cells
as to how the moisture of the polymer membrane can be kept for
acquiring better conduction efficiency out of ions. Please refer to
U.S. Pat. Nos. 5,484,666, 6,190,793 and 6,207,312 for detailed
structures of PEMFC, bipolar plates and MEAs thereof.
According to the psychrometric chart, the moisture for fully
saturated air increases curvingly as temperature rises. For
example, under the constant temperature of 25.degree. C., the
partial pressure for saturated water vapor is 0.032 kg/cm.sup.2,
whereas under the constant temperature of 65.degree. C., the
partial pressure for saturated water vapor reaches 0.245
kg/cm.sup.2. Since the operational temperature for PEMFCs is
between 60.degree. C. to 85.degree. C., air before being introduced
into a fuel cell may be fully saturated already, yet as such air is
introduced into a fuel cell, the relative moisture for such air is
swiftly lowered by heightened temperature, thus such air is caused
to have strong moisture absorption capacity after entering a fuel
cell. Therefore, as such air enters a fuel cell, such air
immediately absorbs the internal moisture of the fuel cell when
contacting the polymer membrane therein, thus causing the polymer
membrane to contain such a low degree of moisture that not only
decreases the conduction capacity of the membrane ions but also
decreases the efficiency of the fuel cell.
Therefore, it is crucial for the efficiency of fuel cells to
properly heat and moisturize air before such air enters fuel cells.
Since the moisture-containing capacity of air increases as
temperature rises, sufficient heating of air should correspondently
proceed as air is moisturized. Consequently, it is crucial for
increasing the efficiency of fuel cells as to how air or oxygen
entering fuel cells can be moisturized and heated. In addition,
high-temperature and high-moisture air discharged from the negative
electrode in the fuel cell or a fuel processor generating hydrogen
can be utilized as the best means for pre-heating air/oxygen. Thus
it is the most direct and effective way to moisturize and heat the
system air by utilizing directly pure water (or water vapor)
yielded from the fuel cell (negative electrode). Generally, total
heat exchangers are utilized for effective exchange of temperature
and moisture, which means the effective exchange of both the
sensible heat and the latent heat is acquired simultaneously via
total heat exchangers.
The conventional total heat exchangers provide the rotor adsorption
and permeable membrane designs, wherein the working principle for
the rotor adsorption design is to utilize all kinds of
moisture-absorbing material as media for transferring moisture and
heat, the total heat exchanging rotor is then caused to rotate
through an external generator, thus achieving the exchange of
moisture and heat from both the cool and hot airflows, whereas the
working principle for the permeable membrane design is to select a
material permeable by moisture but not by air or a micro-porous
material having excellent moisture-absorbing capacity as the
membrane to be placed between a dry and cool airflow and a moist
and hot airflow, thus achieving the exchange of water and heat.
However, when applied in fuel cell systems, the total heat
exchanger with rotor adsorption design is to cause numerous
drawbacks, for example, the selection of adsorbents has to be
extremely cautious since adsorbents cause tremendous impact on the
function of fuel cells, therefore, once an alkali compound is
chosen as the adsorbent, the function of fuel cells is to be
adversely affected tremendously with the battery life thereof being
significantly limited; furthermore, the cost of utilizing the total
heat exchanger with rotor adsorption design is higher and power is
needed for generating rotors, thus the electricity expenses for
fuel cells become more difficult to be lowered, not to mention the
efficiency for the total heat exchanger with rotor adsorption
design is generally lower than 50%.
On the other hand, when applied in fuel cell systems, the total
heat exchanger with permeation membrane design provides better
exchanging effect between water and heat with the cost thereof
being lower than that of the total heat exchanger with rotor
adsorption design, yet since membrane material is mostly made of
polymer or porous material, the heat conductability thereof is to
be lower than that of metal material; furthermore, since porous
material is utilized as the membrane, when under the conditions of
the membrane having large area and the pressure difference being
constant on the two sides, gases on both sides having pressure
differences are to permeate therethrough, consequently the pores of
the membrane are to be clogged either by being deformed through
containing moisture or by being accumulated with minute particles
in the air, thus causing the system to be unstable and the function
thereof to be difficult to control.
Therefore, both conventional humidifying devices applied in fuel
cells cause drawbacks requiring improvements.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a
humidifier having a housing wherein a first gas passage for dry and
cool oxygen/air to pass through before entering the fuel cell, and
a second gas passage for conveying high-temperature and
high-moisture exhaust gas discharged by the fuel cell are disposed,
thus through heat exchanging plates mounted between the first and
second gas passages, water and heat in the exhaust gas of the
second gas passage are recycled and conveyed to the first gas
passage to achieve the humidification effect and increase the
efficiency of the fuel cell.
A humidifier capable of achieving the foregoing objects comprises a
housing, heat exchanging plates, water-trapping reservoirs and
water absorbable and permeable material, wherein the interior of
the housing is divided into a first gas passage and a second gas
passage, with the first and second gas passages respectively having
gas inlets and gas outlets, and water saturation apertures are
mounted underneath the heat exchanging plates and water-trapping
reservoirs are mounted underneath the water saturation apertures,
with water absorbable and permeable material filled in the
water-trapping reservoirs.
Preferably, the gas inlet for the first passage of the present
invention is for conveying air or oxygen therein, whereas the gas
outlet communicates with the air or oxygen inlet of the fuel cell,
the gas inlet of the second gas passage is for conveying therein
high-temperature and high-moisture exhaust gas having lower oxygen
content, and the gas outlet of the second gas passage is for
discharging the exhaust gas after being cooled
Preferably, the heat-exchanging plates are made of metal, and the
surface of the heat-exchanging plates facing towards one side of
the first gas passage are the evaporation surface and the surface
of the heat-exchanging plates facing towards one side of the second
gas passage are the condensation surface; the condensation surface
may condense moisture in the exhaust gas in the second gas passage
into water drops which flow via the water saturation apertures to
the evaporation surface and are evaporated in the first gas passage
so as to moisturize air or oxygen in the first gas passage.
Preferably, the heat-exchanging plates are vertically mounted, and
at least one heat-exchanging plate is mounted.
Preferably, the water-trapping reservoirs of the present invention
can be formed as U shape, L shape, H shape or V shape, so as to
trap water drops condensed in the second gas passage; at least one
such water-trapping reservoir is mounted.
Preferably, the location of the water-trapping reservoirs on one
side of the second gas passage is higher than that of the water
saturation apertures.
Preferably, the water permeable stuffing material, such as
non-woven fabrics or porous pottery and porcelain material, is
disposed in the first gas passage.
Preferably, the evaporation surface of the heat-exchanging plates
of the present invention are disposed with a plurality of fins for
increasing the evaporation area.
Preferably, the evaporation surface of the heat-exchanging plates
are coarsely processed so as to increase the evaporation area.
Preferably, the condensation surface of the heat-exchanging plates
are disposed with a plurality of fins so as to increase the
heat-conducting area.
Preferably, the condensation surface of the heat-exchanging plates
are hydrophobically processed, which refers to the application of a
layer of Teflon membrane thereon, so as to cause the condensation
water to speedily slide downwards.
Preferably, the first gas passage is fully filled with the water
permeable stuffing material, such as non-woven fabrics or porous
pottery and porcelain material.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects and advantages of the present
invention will become better understood with regard to the
following description, appended claims and accompanying drawings
that are provided only for further elaboration without limiting or
restricting the present invention, where:
FIG. 1 shows an externally perspective view of the present
invention;
FIG. 2 shows a sectional structural view from the left side of the
humidifier in FIG. 1;
FIG. 3 shows a plain-surface structural view of the heat-exchanging
plate in the present invention;
FIG. 4 shows a schematic diagram regarding the integration between
the present invention and a fuel cell;
FIG. 5 shows a sectional structural view of air (or oxygen) and
exhaust gas being conveyed into the present invention shown in FIG.
4;
FIG. 6 shows another embodiment for the heat-exchanging plate and
water-trapping reservoirs of the present invention;
FIG. 7 shows a plain-surface structural view of the heat-exchanging
plate embodied in FIG. 6;
FIG. 8 shows a perspective view of the condensation surface with
fins disposed thereon of the heat-exchanging plate of the present
invention;
FIG. 9 shows a perspective view of the evaporation surface with
fins disposed thereon of the heat-exchanging plate of the present
invention;
FIG. 10 shows a perspective view of the evaporation surface of the
heat-exchanging plate of the present invention after being coarsely
processed; and
FIG. 11 shows a schematic diagram of a plurality of the present
invention connected in parallel to form a multi-module
assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The following is a detailed description of the best presently known
modes of carrying out the inventions. This description is not to be
taken in a limiting sense, but is made merely for the purpose of
illustrating the general principles of the inventions.
Please refer to FIGS. 1 to 3, the humidifier 1 of the present
invention comprises a housing 10, a plurality of heat-exchanging
plates 11, water permeable stuffing material 18, a plurality of
water-trapping reservoirs 20 and a plurality of water absorbable
and permeable material 21, wherein the plurality of heat-exchanging
plates 11 are vertically fixated within the housing 10 and divide
the interior of the housing 10 into a first gas passage 12 and a
second gas passage 13, a gas inlet 14 and a gas outlet 15 are
respectively formed underneath and on top of the first gas passage
12, and a gas outlet 17 and a gas inlet 16 are respectively formed
underneath and on top of the first gas passage 12; one side of each
heat-exchanging plate 11 facing the first gas passage 12 is an
evaporation surface 111 and another side of each heat-exchanging
plate 11 facing the second gas passage 13 is a condensation surface
110, and at least one water saturation aperture 19 is disposed
underneath most heat-exchanging plates 11; the water-trapping
reservoirs 20 are correspondingly mounted underneath the
heat-exchanging plates 11 having water saturation apertures 19, and
the location of the water-trapping reservoirs 20 on one side of the
second gas passage 13 is higher than that of the water saturation
apertures 19; the water absorbable and permeable material 21 is to
fill the water saturation apertures 19 underneath the
heat-exchanging plates 11, and the water permeable stuffing
material 18 is placed in the first gas passage 12.
The operational procedure of the humidifier 1 of the present
invention is to be elaborated in accordance with FIGS. 4 and 5.
As shown in FIG. 4, a common fuel cell 100 comprises a gas-burning
inlet 101, a gas-burning tail gas inlet 102, an oxygen/air inlet
103 and an exhaust gas outlet 104, and the humidifier 1 of the
present invention is to be connected to the fuel cell 100 with
means of vertical fixation via certain conduits, which means the
gas outlet 15 of the humidifier 1 is connected to the oxygen/air
inlet 103 of the fuel cell 100 via conduits, and the gas inlet 16
is connected to the exhaust gas outlet 104 via conduits. Please
refer to FIG. 4, dry and cool oxygen/air is conveyed through the
gas inlet 14 of the humidifier 1 into the first gas passage 12, and
then such oxygen/air is caused to flow to the oxygen/air inlet 103
of the fuel cell 100 through the water permeable stuffing material
18, subsequently, with the operation of the fuel cell 100,
high-moisture and high-temperature exhaust gas generated by the
fuel cell 100 is conveyed via the exhaust gas 104 to the gas inlet
16 of the humidifier 1 and then caused to enter into the second gas
passage 13.
Since the first and second gas passages 12 and 13 are divided by
the heat-exchanging plates 11 which are made of metal (for metal
provides high heat conduction coefficient), as moist and hot
exhaust gas in the second gas passage 13 gets into contact with the
high-efficiency heat conduction surface of the heat-exchanging
plates 11 (the condensation surface 110), heat energy of moist and
hot exhaust gas is conveyed to the first gas passage 12 via the
condensation surface 110 to meet the dry and cool oxygen/air
therein since the temperature of the moist and hot exhaust gas is
higher than that on the condensation surface 110, thus achieving
the effect of heating oxygen/air drawn in and cooling the moist and
hot exhaust gas. To elaborate in more detail, since the moist and
hot exhaust gas is swiftly cooled by the condensation surface 110
of the heat-exchanging plates 11, moisture thereof is then
condensed into the condensation water 3 that subsequently slides
downwardly along the condensation surface 110 due to the
gravitational force to the U-shaped water-trapping reservoirs 20
and is kept therein, eventually both sides of the water saturation
apertures are submerged by water. For avoiding airflows on both
sides are to crossflow due to the pressure difference,
water-trapping reservoirs 20 are further placed with water
absorbable and permeable material 21 such as non-woven fabrics or
porous pottery and porcelain material, such that the condensation
water 3 is drawn by the absorption force from the water absorbable
and permeable material 21 into the first gas passage 12 so as to
avoid the crossflow by airflows on both sides.
The water permeable stuffing material 18 is made of porous stuffing
material such as non-woven fabrics or porous pottery and porcelain
material, such that the condensation water 3 is proportionally
distributed on the evaporation surface 111 of the heat-exchanging
plate 11 and the contact area between water and air is increased,
the condensation water 3 is consequently absorbed swiftly by
oxygen/air drawn in, and the synchronized conveyance of heat and
the humidification effect for oxygen/air are both improved.
Therefore, as shown in FIG. 5, water and heat in exhaust gas in the
second gas passage 13 are recycled by the heat-exchanging plate 11
and transferred to the first gas passage 12, thus achieving the
humidification effect for oxygen/air drawn in, so as to increase
the efficiency of the fuel cell.
The objects of mounting a plurality of heat-exchanging plates 11
and a plurality of water-trapping reservoirs 20 are not only for
water permeation and avoiding the crossflow from airflows on both
sides, but also for avoiding the condensation water 3 to continue
accumulating downwardly, thus conducive to reducing the membrane
thickness of the condensation water 3 so as to improve on heat
conduction and condensation efficiency.
Apart from means of round-hole shape (not limited to round holes),
the water saturation apertures 19 of the heat-exchanging plates 11
can be implemented as shown in FIG. 6 and FIG. 7, which refers to
the formation of a slit between two heat-exchanging plates 11 as
the water saturation aperture 190, another design that achieves the
identical object.
FIG. 6 also shows an embodiment wherein the water-trapping
reservoirs 20 have different shapes, that is, the water-trapping
reservoirs 20a can also be formed in L-shape apart from being U
shape as the water-trapping reservoirs 20, and the location of the
water-trapping reservoir 20a on one side of the second gas passage
13 is higher than that of the water saturation apertures 19 (190).
Furthermore, the water-trapping reservoirs 20 can be formed as
H-shaped water-trapping reservoirs 20b, and with the concave
portions 20c and 20d mounted therein, the H-shaped water-trapping
reservoirs 20b can further be held and fixated between the
heat-exchanging plates and those underneath. The location of the
water-trapping reservoirs 20b on one side of the second gas passage
13 is also higher than that of the water saturation apertures
19(190). By the same token, the V-shaped water-trapping reservoirs
not shown in figures can also be embodied in the present
invention.
The heat-exchanging plates 11 of the present invention may be
processed on the condensation surfaces 110 thereof, such as adding
fins 112 to increase the heat conduction area as shown in FIG. 8,
or being hydrophobically processed by applying a layer of Teflon so
as to reduce the adhesion of water drops and, by being conducive to
condensation water's swift sliding downwards, increase the effect
of condensation and heat conduction.
For the purpose of proportionally distributing the condensation
water 3 acquired through permeation by moisture-absorption effect
from the second gas passage 13 via the water saturation apertures
19 on the metal evaporation surface 111, thus absorbed by
oxygen/air drawn in so as to acquire the humidification effect,
fins 113 can be mounted on the evaporation surface 111 so as to
increase the heat conduction area as shown in FIG. 9. Or the
evaporation surface 111 can be applied with adequate metal
evaporation and heat conduction processing such as coarsely
processed as shown in FIG. 10, such that the condensation water 3
can easily be evaporated and subsequently be absorbed by dry and
cool oxygen/air drawn in, so as to increase the adhesion of the
liquidized water, thus be conducive to allowing the liquidized
water to form a membrane and therefore enhance the evaporation and
heat conduction effect.
The humidifier 1 of the present invention is modularly designed for
adjusting to power generation systems in fuel cells having
different power generation capacities. The outer appearance of the
single module of the present invention is shown in FIG. 1, and the
multiple-module design is formed in parallel as shown in FIG. 11,
which also simplifies the design and assembling procedures and thus
reduces the production cost.
Although the present invention has been described in considerable
detail with reference to certain preferred embodiments thereof,
those skilled in the art can easily understand that all kinds of
alterations and changes can be made within the spirit and scope of
the appended claims. Therefore, the spirit and scope of the
appended claims should not be limited to the description of the
preferred embodiments contained herein.
* * * * *